A. Field of the Invention
This invention relates to hand-held calculators and in particular to hand-held calculators which perform numeric calculations in feet, inches and fractions of inches and which display the results also in feet, inches, and fractions of inches without the necessity of first changing the numbers into a decimal format.
B. Background Art
Portable hand-held electronic calculators are well known and readily available in the marketplace. Typically, these calculators have a housing containing a display, a keyboard for entering numerical values, a keyboard for entering functions such as arithmetic operations, and a microprocessor or the like contained therein for performing a number of predetermined computations based upon which keys in the numerical and functional keyboard are pressed.
A portable hand-held electronic calculator is needed for performing calculations in feet, inches, and fractions of an inch, and for displaying the results in feet, inches and fractions in a conventional and recognizable format. It is adapted to perform in a manner that is particularly useful to the home handyman, the construction industry and the many trades and professions where feet, inches, and fractions are the standard units of measurement. Complex, confusing, and error ridden calculations involving feet, inches, and fractions of an inch, such as multiplication, division, addition, subtraction, squares and square roots, can be performed directly without first converting the numbers into a decimal format. A specialized display is further desired which allows the user to keep track of his place while making feet, inches and fractions entries. Such a display should prompt the user to manually enter numerical data in a particular sequence related specifically to the way that feet, inches, and fractions are conventionally written and spoken in the construction industry. Accordingly such a calculator may be used both in the home, office and field to perform quickly and efficiently complex calculations in feet, inches, and fractions that are now being performed longhand, thus saving time, reducing error, and reducing building construction costs.
The inventors prior to the filing of this invention, effectuated a patentability search to ascertain the state of the prior art. The results of this search are as follows:
______________________________________ INVENTOR SERIAL NO. ISSUE DATE ______________________________________ Kilby 3,819,921 June 25, 1974 Sampey 3,872,288 March 18, 1975 Kraus 3,895,356 July 15, 1975 Fisher et al 3,934,233 Jan. 20, 1976 Esch 3,858,033 Dec. 31, 1974 Goldsamt 3,973,113 August 3, 1976 Katz et al 3,979,057 Sept. 7, 1976 Katz et al 3,979,058 Sept. 7, 1976 Raymond, Jr. 3,989,939 Nov. 2, 1976 Dickinson et al 4,001,569 Jan. 4, 1977 Boulanger 4,005,293 Jan. 25, 1977 Woo, Jr. et al 4,158,229 June 12, 1979 Kakutani 4,195,348 March 25, 1980 Washizuka 4,213,035 July 15, 1980 Bromley 4,249,744 Feb. 10, 1981 Toal et al 4,051,605 October 4, 1977 ______________________________________
The 1977 patent issued to Dickinson et al (U.S. Pat. No. 4,001,569) sets forth a battery powered hand-held calculator which, among other functions, provides conversion programming routines from one unit of measurement to other units of measurement. Conversion factors are built in so that the user of the hand-held calculator does not have to memorize them.
The 1980 patent issued to Kakutni (U.S. Pat. No. 4,195,348) and the 1980 patent issued to Washizuka et al (U.S. Pat. No. 4,213,035) both relate to an electronic digital scale and calculator. Both approaches utilize a conventional tape measure in connection with electronic circuitry, a keyboard, and a display. In the Kakutni approach, various programs are built in such as conversion programs for conversion to inches or to feet but not to feet and inches! The Washizuka patent includes a program to use the calculator both as a combined protractor and calculator.
The 1979 patent issued to Woo, Jr. et al (U.S. Pat. No. 4,158,229) relates to an electronic roll adding a keyboard, alpha numeric display, and an electronic scale.
The 1975 patent issued to Kraus (U.S. Pat. No. 3,895,356) also relates to an electronic scale or gauging system for performing measurement functions and a programmable calculator with an associated display. A number of programs are built into the side for performing different types of functions.
Finally, the patents issued to Sampey (U.S. Pat. No. 3,872,288) and to Esch (U.S. Pat. No. 3,858,033) both relate to electronic readout apparatuses for distance measuring instruments.
The Katz patent (U.S. Pat. No. 3,979,058) sets forth a prompting system for guiding the operator of the calculator through programming routines by directly indicating when data should be entered and what type of data should be entered. Another Katz patent (U.S. Pat. No. 3,979,057) relates to an electronic navigational computer involving a number of program selector keys which can be selected to achieve the desired result. These selector keys relate to special navigational parameters.
The Kilby et al patent (U.S. Pat. No. 3,819,921) discloses a miniature electronic calculator utilizing an integrated semi-conductor circuit array located in one plane for performing the arithmetic calculations and for generating the control signals.
The Raymond, Jr. patent (U.S. Pat. No. 3,989,939) sets forth an electronic calculator which is ligit oriented and which utilizes both a read only memory for program storage and a random access memory for data storage.
The Boulenger patent (U.S. Pat. No. 4,005,293) relates to a push button keyboard switch assembly for inputting into a hand-held calculator.
The Bromly patent (U.S. Pat. No. 4,249,744) discloses a hand-held electronic device for simulating a two player electronic sports action game.
The Fisher et al patent (U.S. Pat. No. 3,934,233) sets forth a read only memory technique for use in electronic hand-held calculators.
Finally, the Goldsamt patent (U.S. Pat. No. 3,973,113) discusses an electronic calculator for handling feet, inch and fraction numerics. The Goldsamt approach utilizes a separate set of keys for inputting fractional values. The disclosed keys are as follows: 1/8, 1/4, 3/8, 1/2, 5/8, 3/4 and 7/8.
For fractions of a higher resolution an additional key on separate keyboards would have to be provided for each key.
Of all the prior art "patented" approaches set forth above, only the Goldsamt patent relates to a calculator in the same field as the present invention. Goldsamt performs his functions through the use of a "primary core" which corresponds to a conventional functional numerical keyboard. Additionally, a separate "inch core" containing the numbers 1 through 12 is provided. Finally, a "fraction core" setting forth the above listed fractions is provided. Hence, Goldsamt contemplates the use of three separate input keyboards: one for entering feet, one for entering inches, and one for entering fractions of an inch.
The inventors are also aware of a product trademarked "ADDOMETER" and manufactured by the Addometer Company, 14901 Evans, Dolton, Ill. 60419. This product uses a "FT" key for displaying entered numerics as feet, an "IN" key for displaying entered numerics as inches, and a "FR" key for displaying entered numerics as fractions.